This invention relates to an inflatable seat belt apparatus having a webbing at least a portion of which is formed into a bag-like shape, wherein the webbing is maintained in a belt-like form during ordinary conditions and is inflated by gas from gas generating means at the time of an emergency.
The seat of a vehicle such as an automobile often is equipped with a seat belt apparatus. The seat belt apparatus is adapted to restrain a seated passenger by a webbing in the event of an emergency such as a vehicular collision, thereby protecting the passenger against injury caused by a collision. However, in a seat belt apparatus of this kind, the width of the webbing constituting a belt which restrains the passenger cannot be made very large, and therefore a comparatively large load acts upon the passenger locally when the passenger is restrained by the webbing.
In efforts to solve this problem, inflatable seat belt apparatus have been proposed, as disclosed in the specifications of Japanese Patent Application Laid-Open (KOKAI) Nos. 47-26830 and 49-88220, in which the webbing is formed into the shape of a bag and functions as an ordinary seat belt by being maintained in a belt-like form under ordinary circumstances. In the event of an emergency, a gas emitted from gas generating means is introduced into the bag-shaped webbing, thereby inflating the webbing so that the passenger is restrained by the inflated webbing. In accordance with an inflatable seat belt apparatus of this kind, the webbing receives the kinetic energy of the passenger over a wider area. Since the load is thus dispersed, the load which acts upon the passenger becomes comparatively small and the passenger is protected much more effectively.
When it is attempted to furnish a rear seat with an air bag apparatus of the kind provided in order to protect a passenger in the front seat, the air bag apparatus can only be installed in the front of the rear seat. In a case where an air bag apparatus is provided in the front seat, it is difficult to so arrange it that the air bag apparatus in the rear seat will protect the rear passenger properly and effectively since the position of the front seat differs depending upon whether it is moved forward or backward by the passenger, and since the reclining position of the front seat also differs depending upon the passenger. Accordingly, the above-described inflatable seat belt apparatus is particularly useful in the rear seat.
In the seat belt apparatus disclosed in the aforesaid publications, the inflatable webbing is passed through a through-hole provided in a tongue, whereby the tongue is free to slide along webbing. If the webbing becomes twisted or turns over in the tongue, not only is it impossible to apply the webbing correctly but smooth movement of the tongue along the webbing is impeded as well. Accordingly, it is required that the webbing hole formed in the tongue be designed to have a size that will not allow the webbing to become twisted or turned over. This means that there is a limitation upon the size of the hole and that the hole cannot be made very large.
However, if there is a limitation upon the size of the belt hole in the tongue, the inflation of the webbing is restricted by the tongue when the webbing is inflated by inflow of a gas to the bag-shaped webbing from the gas generating means in the event of an emergency. As a result, the injected gas cannot flow into the webbing smoothly from the location of the tongue, namely into the portion of the webbing in contact with the passenger. As a result, there are instances in which the portion of the webbing contacting the passenger is not inflated rapidly and reliably. In particular, since the webbing is folded at the belt through-hole of the tongue, the area of the gas flow passageway cannot be made sufficiently large and hence there is an even greater impediment to smooth flow of the gas.
Thus, if the portion of the webbing in contact with the passenger is not inflated rapidly and reliably, a case is conceivable in which it is impossible to reliably and fully realize the inflatable seat belt function of reducing the load upon the passenger by having the webbing disperse the load attributable to the kinetic energy of the passenger.